Energy expenditure and muscular activation patterns through active sitting on compliant surfaces

AbstractPurposeTo test the effectiveness of sitting surfaces with varied amounts of stability on muscle activity and energy expenditure.MethodsUsing a within-participants repeated measures design, 11 healthy young-adult females (age = 20.0 ± 1.8 years) were measured using indirect calorimetry to assess energy expenditure, and electromyography to assess muscular activation in trunk and leg musculature under three different sitting surfaces: flat-firm surface, air-filled cushion, and a stability ball. Data were analyzed using repeated measures analysis variance with follow-up pairwise contrasts used to determine the specific effects of sitting surface on muscle activation and energy expenditure.ResultsSignificantly greater energy expenditure was recorded for the stability ball (p = 0.01) and the cushion (p = 0.03) over the flat surface (10.4% and 9.6% greater, respectively), with no differences between the ball and the cushion. Both the ball and the cushion produced higher tibialis anterior activation over the flat surface (1.09 and 0.63 root-mean-square millivolts (RMSmv), respectively), while the stability ball produced higher soleus activity over both cushion and flat surfaces (3.97 and 4.24 RMSmv, respectively). Additionally, the cushion elicited higher adductor longus activity over the ball and flat surfaces (0.47 and 0.52 RMSmv, respectively), but no trunk musculature differences were revealed.ConclusionCompliant surfaces resulted in higher levels of muscular activation in the lower extremities facilitating increased caloric expenditure. Given the increasing trends in sedentary careers and the increases in obesity, this is an important finding to validate the merits of active sitting facilitating increased caloric expenditure and muscle activation

Gene Expression Profile and Acute Gene Expression Response to Sclerostin Inhibition in Osteogenesis Imperfecta Bone

Sclerostin antibody (SclAb) therapy has been suggested as a novel therapeutic approach toward addressing the fragility phenotypic of osteogenesis imperfecta (OI). Observations of cellular and transcriptional responses to SclAb in OI have been limited to mouse models of the disorder, leaving a paucity of data on the human OI osteoblastic cellular response to the treatment. Here, we explore factors associated with response to SclAb therapy in vitro and in a novel xenograft model using OI bone tissue derived from pediatric patients. Bone isolates (approximately 2 mm3) from OI patients (OI type III, type III/IV, and type IV, n = 7; non‐OI control, n = 5) were collected to media, randomly assigned to an untreated (UN), low‐dose SclAb (TRL, 2.5 μg/mL), or high‐dose SclAb (TRH, 25 μg/mL) group, and maintained in vitro at 37°C. Treatment occurred on days 2 and 4 and was removed on day 5 for TaqMan qPCR analysis of genes related to the Wnt pathway. A subset of bone was implanted s.c. into an athymic mouse, representing our xenograft model, and treated (25 mg/kg s.c. 2×/week for 2/4 weeks). Implanted OI bone was evaluated using μCT and histomorphometry. Expression of Wnt/Wnt‐related targets varied among untreated OI bone isolates. When treated with SclAb, OI bone showed an upregulation in osteoblast and osteoblast progenitor markers, which was heterogeneous across tissue. Interestingly, the greatest magnitude of response generally corresponded to samples with low untreated expression of progenitor markers. Conversely, samples with high untreated expression of these markers showed a lower response to treatment. in vivo implanted OI bone showed a bone‐forming response to SclAb via μCT, which was corroborated by histomorphometry. SclAb induced downstream Wnt targets WISP1 and TWIST1, and elicited a compensatory response in Wnt inhibitors SOST and DKK1 in OI bone with the greatest magnitude from OI cortical bone. Understanding patients’ genetic, cellular, and morphological bone phenotypes may play an important role in predicting treatment response. This information may aid in clinical decision‐making for pharmacological interventions designed to address fragility in OI. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156449/2/jbm410377_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156449/1/jbm410377.pd

The effects of whole body vibration on the Wingate test for anaerobic power when applying individualized frequencies

Background: Whole-body vibration (WBV) has been proposed as a viable alternative, or adjuvant to exercise for power development in athletes. More recently individualized frequency (I-Freq) has been introduced with the notion that individuals may elicit a greater reflex response to different levels (Hz) of vibration. Purpose: The aim of the study was to evaluate acute WBV as a feasible intervention to increase power in trained cyclists. Additionally, to evaluate the efficacy of utilizing I-Freq as an alternative to 30Hz, a common frequency seen in the literature. Methods: Twelve highly-trained, competitive male cyclists (age= 29.9 yrs ± SD 10.0; body height=175.4 cm ± SD 7.8; body mass= 77.3 kg ± SD 13.9) free of musculoskeletal injury or pathology participated in the study. The Wingate test for anaerobic power was administered on three occasions following a control of no vibration, 30 Hz, and I-freq. Measures of peak power (PP), average power (AP) and rate of fatigue were recorded and compared to the vibratory conditions using separate RM-ANOVA’s. Results: PP, AP, and rate of fatigue were not significantly impacted by 30 Hz and I-Freq vibration interventions (p > 0.05). Conclusion: Acute WBV using the parameters of the present study may not have been practical to elicit an increase in power as potential changes in the highly trained population may have been muted as a function of training status.School of Physical Education, Sport, and Exercise ScienceThesis (M.S.

The effects of whole body vibration on the Wingate test for anaerobic power when applying individualized frequencies

Background: Whole-body vibration (WBV) has been proposed as a viable alternative, or adjuvant to exercise for power development in athletes. More recently individualized frequency (I-Freq) has been introduced with the notion that individuals may elicit a greater reflex response to different levels (Hz) of vibration. Purpose: The aim of the study was to evaluate acute WBV as a feasible intervention to increase power in trained cyclists. Additionally, to evaluate the efficacy of utilizing I-Freq as an alternative to 30Hz, a common frequency seen in the literature. Methods: Twelve highly-trained, competitive male cyclists (age= 29.9 yrs ± SD 10.0; body height=175.4 cm ± SD 7.8; body mass= 77.3 kg ± SD 13.9) free of musculoskeletal injury or pathology participated in the study. The Wingate test for anaerobic power was administered on three occasions following a control of no vibration, 30 Hz, and I-freq. Measures of peak power (PP), average power (AP) and rate of fatigue were recorded and compared to the vibratory conditions using separate RM-ANOVA’s. Results: PP, AP, and rate of fatigue were not significantly impacted by 30 Hz and I-Freq vibration interventions (p > 0.05). Conclusion: Acute WBV using the parameters of the present study may not have been practical to elicit an increase in power as potential changes in the highly trained population may have been muted as a function of training status.Thesis (M.S.)School of Physical Education, Sport, and Exercise Scienc

Bone hydration: How we can evaluate it, what can it tell us, and is it an effective therapeutic target?

Water constitutes roughly a quarter of the cortical bone by volume yet can greatly influence mechanical properties and tissue quality. There is a growing appreciation for how water can dynamically change due to age, disease, and treatment. A key emerging area related to bone mechanical and tissue properties lies in differentiating the role of water in its four different compartments, including free/pore water, water loosely bound at the collagen/mineral interfaces, water tightly bound within collagen triple helices, and structural water within the mineral. This review summarizes our current knowledge of bone water across the four functional compartments and discusses how alterations in each compartment relate to mechanical changes. It provides an overview on the advent of- and improvements to- imaging and spectroscopic techniques able to probe nano-and molecular scales of bone water. These technical advances have led to an emerging understanding of how bone water changes in various conditions, of which aging, chronic kidney disease, diabetes, osteoporosis, and osteogenesis imperfecta are reviewed. Finally, it summarizes work focused on therapeutically targeting water to improve mechanical properties

Enhanced Bone Size, Microarchitecture, and Strength in Female Runners with a History of Playing Multidirectional Sports

Purpose: Female runners have high rates of bone stress injuries (BSIs), including stress reactions and fractures. The current study explored multidirectional sports (MDS) played when younger as a potential means of building stronger bones to reduce BSI risk in these athletes. Methods: Female collegiate-level cross-country runners were recruited into groups: 1) RUN: history of training and/or competing in cross-country, recreational running/jogging, swimming and/or cycling only and 2) RUN+MDS: additional prior history of training and/or competing in soccer or basketball. High-resolution peripheral quantitative computed tomography was used to assess the distal tibia, common BSI sites (diaphysis of the tibia, fibula and 2nd metatarsal), and high-risk BSI sites (base of the 2nd metatarsal, navicular and proximal diaphysis of the 5th metatarsal). Scans of the radius were used as control sites. Results: At the distal tibia, RUN+MDS (n=18) had enhanced cortical area (+17.1%) and thickness (+15.8%) and greater trabecular bone volume fraction (+14.6%) and thickness (+8.3%) compared to RUN (n=14) (all p<0.005). Failure load was 19.5% higher in RUN+MDS (p<0.001). The fibula diaphysis in RUN+MDS had 11.6% greater total area and 11.1% greater failure load (all p≤0.03). At the 2nd metatarsal diaphysis, total area in RUN+MDS was 10.4% larger with greater cortical area and thickness and 18.6% greater failure load (all p<0.05). RUN+MDS had greater trabecular thickness at the base of the 2nd metatarsal and navicular and greater cortical area and thickness at the proximal diaphysis of the 5th metatarsal (all p≤0.02). No differences were observed at the tibial diaphysis or radius. Conclusion: These findings support recommendations that athletes delay specialization in running and play MDS when younger to build a more robust skeleton and potentially prevent BSIs

Metabolic and Skeletal Characterization of the KK/Ay Mouse Model – a Polygenic Mutation Model of Obese Type 2 Diabetes

Type 2 diabetes (T2D) increases fracture incidence and fracture-related mortality rates (KK.Cg-Ay/J. The Jackson Laboratory; Available from: https://www.jax.org/strain/002468 ). While numerous mouse models for T2D exist, few effectively stimulate persistent hyperglycemia in both sexes, and even fewer are suitable for bone studies. Commonly used models like db/db and ob/ob have altered leptin pathways, confounding bone-related findings since leptin regulates bone properties (Fajardo et al. in Journal of Bone and Mineral Research 29(5): 1025-1040, 2014). The Yellow Kuo Kondo (KK/Ay) mouse, a polygenic mutation model of T2D, is able to produce a consistent diabetic state in both sexes and addresses the lack of a suitable model of T2D for bone studies. The diabetic state of KK/Ay stems from a mutation in the agouti gene, responsible for coat color in mice. This mutation induces ectopic gene expression across various tissue types, resulting in diabetic mice with yellow fur coats (Moussa and Claycombe in Obesity Research 7(5): 506-514, 1999). Male and female KK/Ay mice exhibited persistent hyperglycemia, defining them as diabetic with blood glucose (BG) levels consistently exceeding 300 mg/dL. Notably, male control mice in this study were also diabetic, presenting a significant limitation. Nevertheless, male and female KK/Ay mice showed significantly elevated BG levels, HbA1c, and serum insulin concentration when compared to the non-diabetic female control mice. Early stages of T2D are characterized by hyperglycemia and hyperinsulinemia resulting from cellular insulin resistance, whereas later stages may feature hypoinsulinemia due to β-cell apoptosis (Banday et al. Avicenna Journal of Medicine 10(04): 174-188, 2020 and Klein et al. Cell Metabolism 34(1): 11-20, 2022). The observed hyperglycemia, hyperinsulinemia, and the absence of differences in β-cell mass suggest that KK/Ay mice in this study are modeling the earlier stages of T2D. While compromised bone microarchitecture was observed in this study, older KK/Ay mice, representing more advanced stages of T2D, might exhibit more pronounced skeletal manifestations. Compared to the control group, the femora of KK/Ay mice had higher cortical area and cortical thickness, and improved trabecular properties which would typically be indicative of greater bone strength. However, KK/Ay mice displayed lower cortical tissue mineral density in both sexes and increased cortical porosity in females. Fracture instability toughness of the femora was lower in KK/Ay mice overall compared to controls. These findings indicate that decreased mechanical integrity noted in the femora of KK/Ay mice was likely due to overall bone quality being compromised

Tracking changes of individual cortical pores over 1 year via HR-pQCT in a small cohort of 60-year-old females

Introduction: High-resolution peripheral quantitative computed tomography (HR-pQCT) is a powerful tool that has revolutionized 3D longitudinal assessment of bone microarchitecture. However, cortical porosity, a common characteristic of cortical bone loss, is still often determined by static evaluation of overall porosity at one timepoint. Therefore, we sought to 1) describe a technique to evaluate individual cortical pore dynamics in aging females over one year using HR-pQCT imaging and 2) determine whether formation and expansion of pores would exceed contraction and infilling of pores. Methods: HR-pQCT (60.7 μm resolution) images were acquired one year apart at the distal tibia and distal radius in seven female volunteers (60-72 years of age). Baseline and one-year images were registered at each bone site and a custom software was used to quantify dynamic activity of individual cortical pores using the following categories: developed, infilled, expanded, contracted, and static. Results: Over the one-year period, cortical pores actively developed, contracted, expanded, and infilled. More pores expanded and developed vs. infilled or contracted leading to increased pore area in both tibial and radial sites (p = 0.0034 and p = 0.0474, respectively). Closed pores in the tibia, those that were not connected to the endosteal or periosteal surfaces, were the most dynamic of any pores type (open/closed) at either bone site. Conclusion: This study demonstrates an approach to longitudinally track individual cortical pore activity in tibial and radial sites. These data expand conventional parameters for assessing cortical porosity and show increased porosity in one year of aging is caused by newly developed pores and expansion of existing pores

Am I big boned? Bone length scaled reference data for HRpQCT measures of the radial and tibial diaphysis in White adults

Cross-sectional size of a long bone shaft influences its mechanical properties. We recently used high-resolution peripheral quantitative computed tomography (HRpQCT) to create reference data for size measures of the radial and tibial diaphyses. However, data did not take into account the impact of bone length. Human bone exhibits relatively isometric allometry whereby cross-sectional area increases proportionally with bone length. The consequence is that taller than average individuals will generally have larger z-scores for bone size outcomes when length is not considered. The goal of the current work was to develop a means of determining whether an individual's cross-sectional bone size is suitable for their bone length. HRpQCT scans performed at 30 % of bone length proximal from the distal end of the radius and tibia were acquired from 1034 White females (age = 18.0 to 85.3 y) and 392 White males (age = 18.4 to 83.6 y). Positive relationships were confirmed between bone length and cross-sectional areas and estimated mechanical properties. Scaling factors were calculated and used to scale HRpQCT outcomes to bone length. Centile curves were generated for both raw and bone length scaled HRpQCT data using the LMS approach. Excel-based calculators are provided to facilitate calculation of z-scores for both raw and bone length scaled HRpQCT outcomes. The raw z-scores indicate the magnitude that an individual's HRpQCT outcomes differ relative to expected sex- and age-specific values, with the scaled z-scores also considering bone length. The latter enables it to be determined whether an individual or population of interest has normal sized bones for their length, which may have implications for injury risk. In addition to providing a means of expressing HRpQCT bone size outcomes relative to bone length, the current study also provides centile curves for outcomes previously without reference data, including tissue mineral density and moments of inertia

Ex vivo Exposure to Calcitonin or Raloxifene Improves Mechanical Properties of Diseased Bone through Non-cell Mediated Mechanisms

Raloxifene (RAL) reduces clinical fracture risk despite modest effects on bone mass and density. This reduction in fracture risk may be due to improved material level-mechanical properties through a non-cell mediated increase in bone hydration. Synthetic salmon calcitonin (CAL) has also demonstrated efficacy in reducing fracture risk with only modest bone mass and density improvements. This study aimed to determine if CAL could modify healthy and diseased bone through cell-independent mechanisms that alter hydration similar to RAL. 26-week-old male C57BL/6 mice induced with chronic kidney disease (CKD) beginning at 16 weeks of age via 0.2 % adenine-laced casein-based (0.9 % P, 0.6 % C) chow, and their non-CKD control littermates (Con), were utilized. Upon sacrifice, right femora were randomly assigned to the following ex vivo experimental groups: RAL (2 μM, n = 10 CKD, n = 10 Con), CAL (100 nM, n = 10 CKD, n = 10 Con), or Vehicle (VEH; n = 9 CKD, n = 9 Con). Bones were incubated in PBS + drug solution at 37 °C for 14 days using an established ex vivo soaking methodology. Cortical geometry (μCT) was used to confirm a CKD bone phenotype, including porosity and cortical thinning, at sacrifice. Femora were assessed for mechanical properties (3-point bending) and bone hydration (via solid state nuclear magnetic resonance spectroscopy with magic angle spinning (ssNMR)). Data were analyzed by two-tailed t-tests (μCT) or 2-way ANOVA for main effects of disease, treatment, and their interaction. Tukey's post hoc analyses followed a significant main effect of treatment to determine the source of the effect. Imaging confirmed a cortical phenotype reflective of CKD, including lower cortical thickness (p < 0.0001) and increased cortical porosity (p = 0.02) compared to Con. In addition, CKD resulted in weaker, less deformable bones. In CKD bones, ex vivo exposure to RAL or CAL improved total work (+120 % and +107 %, respectively; p < 0.05), post-yield work (+143 % and +133 %), total displacement (+197 % and +229 %), total strain (+225 % and +243 %), and toughness (+158 % and +119 %) vs. CKD VEH soaked bones. Ex vivo exposure to RAL or CAL did not impact any mechanical properties in Con bone. Matrix-bound water by ssNMR showed CAL treated bones had significantly higher bound water compared to VEH treated bones in both CKD and Con cohorts (p = 0.001 and p = 0.01, respectively). RAL positively modulated bound water in CKD bone compared to VEH (p = 0.002) but not in Con bone. There were no significant differences between bones soaked with CAL vs. RAL for any outcomes measured. RAL and CAL improve important post-yield properties and toughness in a non-cell mediated manner in CKD bone but not in Con bones. While RAL treated CKD bones had higher matrix-bound water content in line with previous reports, both Con and CKD bones exposed to CAL had higher matrix-bound water. Therapeutic modulation of water, specifically the bound water fraction, represents a novel approach to improving mechanical properties and potentially reducing fracture risk